The invention relates to a process for the preparation by crushing of scrap comprising metal parts provided with a surface coating.
Such a process is known from EP-A-125,435, this process working in such a way that the metal parts to be prepared are fed to a coarse crusher and crushed to a particle size of 1 mm to 20 mm. The coarse fraction is fed to a fine crushing, on which the coarse fraction is crushed to a particle size of about 300 .mu.m, after which the solid mixture of metal fraction and non-metal fraction is separated in sifters into the metal fraction and the non-metal fraction. The non-metal fraction is agglomerated and the metal fraction is led away for further processing.
In the production and processing of metal-plastic composite sheets in particular large quantities of scrap occur, for example trimming strips, punching remains or deficient charges. Due to the increasing environmental awareness of consumers, it must be expected that used metal-plastic composite sheets will be increasingly collected and returned to the producer. Until now, such scrap has usually been stored on special dumps or fed to refuse incineration installations.
However, metal-plastic composite sheets contain valuable raw materials, which it is intended to recycle. In this respect, industrial scrap is of particular interest, since it is usually free from impurities and can be collected purely by types.
The known proposals for the recycling of scrap comprising metal parts provided with a surface coating can be divided into those in which a separation into metal fraction and coating fraction is not performed a for example, according to German Offenlegungsschrift 3,110,054, metal-plastic composite sheet scrap is further processed in granulated form, and those in which essentially only one component of the scrap material, usually the metallic component, is recovered, for example, according to JP 53,004,079, by heat treatment of the metal-plastic composite sheet at temperatures in the range of the decomposition of the plastic.
All such proposals, including the process discussed above, are very complex and/or only allow the reuse of one component of the scrap.